Running the Numbers

We humans are terrific at measuring and recordkeeping— we even know the length of Noah’s ark, in cubits (300) no less. Technology abets this trait, as computers dutifully crunch our numbers, ad, well, infinitum. As a species, however, we are not so good at appraising information to extract its meaning. Confronted with new data, we tend to overemphasize and generalize, often less than critically.

On that cautionary note, what are we dog people to make of a new University of California, Davis, study that examines relationships between early, late or no spay/neuter and several health conditions in Golden Retrievers? How do we apply its conclusions to the animals in our care?

The Davis docs found increased risk of several cancers, hip dysplasia and cranial cruciate ligament tears among sterilized Goldens; the incidence varied according to the sex and age-at-neuter of their subjects. As such, their findings add to a growing library of veterinary literature on the spay/neuter subject. However, the authors are careful to limit their conclusions, as should we.

First, the findings are breed-specific. Goldens, a highly inbred line, were chosen in part because of their susceptibility to cancers and joint issues. The gene pool was further limited by a study sample of dogs (759, to be precise) seen at the UC Davis clinic, in northern California.

Second, we need to remind ourselves that risk is not destiny, and that correlation is not causation. The study notes that the risk of one type of canine cancer quadrupled in late-neutered females, but also reveals that its incidence grew from 1.6 to 7.4 percent— meaning that about 93 percent of the subjects did not contract the disease.

The authors also indicate that they did not specifically consider obesity, another known factor in dysplasia and cancers. Neutered dogs do tend to be heavier, but we can manage that risk by controlling food intake and quality. We also need to recognize that other studies have noted countervailing positive health effects, as spay/neuter reduces or eliminates rates of other common diseases, such as mammary cancers and uterine infections.

Third, context is crucial. These data feed into the universe of things that are harmful to canines. We know, for example, that nationwide, some 50 percent of the animals in shelters don’t survive the experience. To the extent that intact canines contribute litters to the shelter population, that risk dwarfs exposure to accidents or disease. Shelter “save” rates are improving in many places, but we remain far from a no-kill equilibrium. Job One for canine partisans (including the veterinary community) remains the imperative to reduce that carnage.

After sheltering, risk-of-death varies widely by age and breed. A comprehensive University of Georgia study of vet-reported deaths (“Mortality in North American Dogs from 1984 to 2004,” published in 2011) identifies infections, trauma and birth defects as primary culprits in young dogs, with tumor-related diseases at various breed-specific rates, distantly followed by trauma and infections, which dominate the tally for the late-in-lifespan.

Finally, there are the behavioral and other risk implications of fertility, including management of ardent males and bitches in heat.

The Davis study is a significant contribution to our understanding of the unintended consequences of fertility management in a useful and popular breed. Reproductive organs contribute hormones for many reasons—it would be surprising if their removal were completely trivial. Alternatives to traditional spay/neuter do exist, but they are rarely performed. Injectable sterilizers and contraceptives are coming on the market (they, of course, will carry their own measurable side effects).

It’s important to recognize the limitations of the study: one breed, one gene pool, defined conditions and their rank among all the calamities that can befall our best friends. The study itself notes that spay/neuter is uncommon in Europe, which would appear to open up a range of comparative research possibilities and fertility management options.

We should add the Davis work to the burgeoning database. But until a lot more measurements have been taken from which broader conclusions may be drawn, the best advice is not general to all dogs, but individualized: choose your canine companions carefully and love and support them well, and completely. And recognize that we can’t measure or control for everything, yet—or ever.